U.S. Pat. No. 5,940,545 by Kash and Tsang describes the use of photon timing detection to determine the switching time of transistors in a semiconductor integrated circuit. Kash et al. describe how typical digital circuits will only emit photons during the switching transient. These photons are detected and the arrival time is recorded. Two techniques are described. Both techniques utilize a time-to-amplitude converter and a multi-channel analyzer to determine the photon arrival time and sort the collected data into a time histogram. The first technique utilizes a single avalanche photodiode with a fiber optic probe placed over the sampling area as the photon detection arrangement. The second utilizes a micro-channel plate array detector with standard microscope optics as the photon detection arrangement. In addition, the second technique utilizes position detection electronics to determine the transverse (XY) location of the detected photon. Kash et al. also describe placing the avalanche photodiode at the position of the micro-channel plate in the microscope arrangement to act as a single point detector.
U.S. Pat. No. 6,608,494 by Bruce et al. describes an improvement on Kash et al. with the addition of an ‘aperture element’ 208, and otherwise appears to be identical. The use of apertures in optical systems has been widely known for some time. Bruce et al. indicate the potential use of a scanning laser microscope in their arrangement, but do not explicitly indicate how such a system would be configured (column 3, lines 54-58). Specifically, the issue of how to co-align the laser imaging portion of the microscope with the photon-emission portion of the microscope needed to point at the target is not addressed.
Both the above inventions require a separate means of imaging the integrated circuit in order to determine the actual physical location on the circuit that corresponds to the detected emission photons. That is to say an array camera (e.g. a CCD) or some other imaging means is needed to supply navigation to the area of interest and to determine the photon emission location. Although not explicitly indicated, both inventions require some mechanical means to point the detector at the area of interest on the integrated circuit into the detection field of view. For a single point detector and the scale size of current integrated circuits; expensive, high-precision mechanical stages with sub-micron positioning accuracy are required to achieve the required pointing.
It is the purpose of the current invention to eliminate the need for:
An aperture in the image plane that requires placement over the detection area;
An independent imaging system for navigation and pointing; and
The requirement for high-precision mechanical translation stages.
It is the further purpose of the current invention to allow multiple detection paths that can be conveniently co-aligned and pointed at a target.